I am trying to access the Xtext model of another file during validation. I found several topics about this, but none of them finally worked for me.. So I would be very thankful for hints.

I have DSLs A (Cod) and B (Sod), they do not rely on each other, but A uses information from B during validation.

Following Christian's answer to validation, I read all exported Objects of a certain type. It works, but all the exported Objects return proxies, and I don't know when and how to resolve them. I need not only the qualifiedName, but some other features (Lists).

This works, but as the doc suggests, this solution is not aware of unsaved editor changes (and not even saved changes). What would be the intended way to access the neighbor DSL file in this case, please?

P.S. I cannot find the class XtextResourceSetProvider as suggested by Sebastian, what plugin would it be in?

This resolution (in the validator of DSL A) is working, but only for the "direct" features of SodModel (DSL B). References to another Entity of DSL C, which both A and B reference to, are proxies again. The linking succeeds, but I think I am accessing the resources of DSL B not the correct way in the validator of DSL A.

in the editor the resource set depends on the project to work properly (IResourceSetProvider). if you create a new one
you have to use a project specific which is tricky since validation
is a runtime and not a ui concept

=> you would need a utility that gives you the resourceset for runtime and ui